POCSAG: Allow all 128 ASCII characters to be transmitted

To allow all 128 ASCII characters, a null-terminated string cannot be
used. Instead a length is used to define string length, to allow
null-character in that the message string.

The print function in frame.c is improved and used to present the
string.

src/pocsag/main.c

@@ -224,10 +224,9 @@ static void myhandler(void)
 		}
 		/* send msg */
 		if (i < pos) {
-			buffer[i] = '\0';
 			pos = 0;
 			if (tx)
-				pocsag_msg_send(language, buffer);
+				pocsag_msg_send(language, buffer, i);
 			else
 				LOGP(DPOCSAG, LOGL_ERROR, "Failed to send message, transmitter is not enabled!\n");
 		}